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Great Sand Dunes National Park & Preserve

Colorado · Established September 24, 2004

North America's tallest dunes, piled against snowcapped peaks

Area: 107,346 acres
Established: September 24, 2004
Recreation visits: 432,498 / yr
State: Colorado
Established: September 24, 2004 (national monument 1932)
Area (national park): 107,346 acres (434 km²); about 149,000 acres with the preserve

Great Sand Dunes Weather Forecast

Loading the National Weather Service forecast for Great Sand Dunes…

Seven-day outlook at the park's reference point (37.793, -105.592). Elevation changes everything in the mountains — expect colder, windier and wetter conditions on high ground.

Map of Great Sand Dunes National Park & Preserve

The Park

At the eastern edge of Colorado's San Luis Valley, a sea of sand piles up against the Sangre de Cristo Mountains. The dunes rise as high as 750 ft above the valley floor, the tallest in North America, and behind them alpine peaks climb to more than 13,000 ft. Few places pack desert, forest, wetland and tundra so tightly together.

Great Sand Dunes was proclaimed a national monument in 1932 and became a national park on September 24, 2004, with an adjoining preserve that reaches up to the crest of the range. In late spring the snowmelt of Medano Creek flows in rhythmic surges along the base of the dunes, and children splash in a shallow river on the edge of what looks like the Sahara.

Geography

The dunefield covers about 30 square miles and holds more than a cubic mile of sand. It sits in a natural pocket where the valley's prevailing southwest winds meet the mountain wall and funnel toward three low passes, Mosca, Medano and Music. Storm winds from the northeast push back, so the dunes grow upward rather than migrating away.

Elevations run from about 7,515 ft on the valley floor to 13,604 ft at Tijeras Peak in the preserve. Medano Creek and Sand Creek wrap around the dunefield, carrying sand back toward the valley so the wind can return it to the dunes. Beyond the sand lie a sand sheet of grasses and shrubs and the salty, seasonally wet flats known as sabkha.

Star Dune is often cited as the tallest dune in the park, while nearby High Dune is the more common hiking goal. The combined park and preserve protect about 149,000 acres, from sand sheet to alpine lakes and tundra.

Landmarks

Star DuneDuneA star-shaped dune built by winds from several directions, among the tallest in North America.
High DuneDuneA popular hiking destination on the first ridge of dunes with sweeping views of the dunefield.
Medano CreekRiverA seasonal creek along the dunes whose snowmelt flows in pulsing surges in late spring.
Mosca PassValleyOne of three low passes that funnel wind and help trap sand in the dunefield.
Medano PassValleyA mountain pass at the head of Medano Creek reached by a rugged four-wheel-drive road.
Mount HerardPeakA prominent peak rising behind the dunes in the national preserve.
Tijeras PeakPeak · 13,604 ftThe highest point in the park and preserve, in the Sangre de Cristo Mountains.

Geology

The San Luis Valley is part of the Rio Grande Rift, a place where the crust has been pulling apart and sinking while the Sangre de Cristo Mountains rise on its eastern flank. Over millions of years, sediment washed down from the San Juan Mountains to the west and from the Sangre de Cristos to the east, filling the valley floor.

For long stretches, much of that sediment settled in large lakes, including one known as Lake Alamosa. About 440,000 years ago the lake drained south, carving a path that became the Rio Grande Gorge. As later lakes and streams dried and shrank, wind picked up the exposed sand and swept it northeast toward the mountain wall.

The dunes today are held in place by a balance of forces. Prevailing southwest winds push sand toward the mountains, storm winds from the northeast push it back, and Medano and Sand creeks carry sand around the edges and return it downwind. Groundwater keeps the sand moist a short way beneath the surface, and dating of dune deposits shows sand grains buried for anywhere from a few hundred to tens of thousands of years.

Deep time

Millions of years agoRifting began lowering the San Luis Valley while the Sangre de Cristo Mountains rose.
Hundreds of thousands of years agoSediment from the San Juan and Sangre de Cristo mountains accumulated in valley lakes, including Lake Alamosa.
About 440,000 years agoLake Alamosa drained south, helping carve the Rio Grande Gorge.
Tens of thousands of years ago to presentWind blew exposed sand northeast into the mountain pocket where the dunes now stand.
PresentOpposing winds and recycling creeks keep the dunes growing upward rather than migrating away.

The rocks

Great Sand Dunes dunefieldLate Pleistocene to present
Wind-deposited sand forming star, reversing and barchan dunes.
Sand sheetLate Pleistocene to present
A broad, grassy apron of sand surrounding the dunefield.
SabkhaHolocene to present
Flats crusted with salts where groundwater evaporates and binds sand.
Sangre de Cristo Mountains bedrockPrecambrian to Paleozoic
Ancient crystalline and sedimentary rock uplifted along the rift's eastern edge.
San Juan volcanic sedimentsCenozoic
Eroded volcanic material from the west that contributes much of the dune sand.

Trees, Plants & Ecosystems

486vascular plant species recorded

DunefieldAbout 7,500–8,700 ft
Shifting sand where only specialized plants and insects, including a tiger beetle found nowhere else, survive.
Sand sheet grasslands and shrublandsValley floor around the dunes
Blowout grass, ricegrass, rabbitbrush and prairie sunflower hold loose sand, with kangaroo rats and pronghorn.
Wetlands and sabkhaValley floor west of the dunes
Seasonal ponds and salty flats fed by groundwater, supporting frogs, shorebirds and elk.
Riparian corridorsMedano and Sand creeks
Cottonwoods and willows follow the creeks from the mountains to the dunes.
Montane and subalpine forest8,000–11,700 ft
Pinyon, ponderosa pine, Douglas fir, aspen and spruce-fir forests on the mountain slopes.
Alpine tundraAbove 11,700 ft
Lakes, meadows and rock slopes near the crest, home to pikas and ptarmigan.

Trees

Ponderosa pinePinus ponderosa var. scopulorumScattered pines in open woodland near the dune margins.
Pinyon pinePinus edulisDominates foothill woodlands with juniper.
Rocky Mountain juniperJuniperus scopulorumA drought-tolerant tree of the lower slopes.
Limber pinePinus flexilisGrows on high, exposed ridges.
Rocky Mountain bristlecone pinePinus aristataA long-lived pine near treeline in the preserve.
Engelmann sprucePicea engelmanniiForms subalpine forest with fir.
Douglas firPseudotsuga menziesiiCommon on montane slopes.
White firAbies concolor var. concolorFound in cooler montane canyons.
Quaking aspenPopulus tremuloidesIts groves light the mountainsides gold in fall.
Narrowleaf cottonwoodPopulus angustifoliaLines the mountain creeks as they emerge toward the dunes.

Wildflowers, shrubs & other plants

Blowout grassRedfieldia flexuosaA pioneer grass that stabilizes shifting sand with long runners.
Indian ricegrassAchnatherum hymenoidesA bunchgrass whose seeds were a traditional food.
Needle and threadHesperostipa comataA grass with long, twisting awns on the sand sheet.
Prairie sunflowerHelianthus petiolarisYellow flowers that bloom on the dunes in late summer.
Rocky Mountain beeplantCleome serrulataPink flower clusters that attract bees in sandy soil.
Rubber rabbitbrushEricameria nauseosaA shrub covered in yellow bloom in late summer.
GreasewoodSarcobatus vermiculatusA salt-tolerant shrub of the valley flats.
Soapweed yuccaYucca glaucaA spiky yucca with cream flower stalks.
Plains pricklypearOpuntia polyacanthaA low cactus with yellow spring blooms.
Skunkbush sumacRhus trilobataA shrub with red, tangy berries in canyon edges.
SaltgrassDistichlis spicataA salt-tolerant grass of wet alkaline flats.
Colorado blue columbineAquilegia caeruleaColorado's state flower, in moist mountain meadows.
Scarlet giliaIpomopsis aggregataRed trumpet flowers in montane openings.

Wildlife

48mammals
197birds
5reptiles
6amphibians
4fish

Mammals

ElkCervus elaphusHerds move between the mountains and valley grasslands.
Mule deerOdocoileus hemionusCommon near the visitor center and campground.
PronghornAntilocapra americanaGrazes the open grasslands of the valley.
Black bearUrsus americanusLives in the forested mountains and sometimes wanders to the dunes.
CoyoteCanis latransTracks often crisscross the dunes at dawn.
Ord's kangaroo ratDipodomys ordiiA nocturnal jumper that never needs to drink, getting water from seeds.
American pikaOchotona princepsLives on high talus slopes in the preserve.
Yellow-bellied marmotMarmota flaviventrisFound in rocky alpine meadows.
Bighorn sheepOvis canadensisUses the steep high country of the Sangre de Cristos.

Birds

Golden eagleAquila chrysaetosHunts over the grasslands and dunes.
Ferruginous hawkButeo regalisA large hawk of open valley country.
Swainson's hawkButeo swainsoniA summer migrant that hunts grasshoppers over grasslands.
Black-billed magpiePica picaA noisy, long-tailed bird near the creeks.
Steller's jayCyanocitta stelleriA crested jay of the montane forest.
Western scrub-jayAphelocoma californicaCommon in pinyon-juniper woodland.
Clark's nutcrackerNucifraga columbianaCaches pine seeds on high slopes.
Mountain bluebirdSialia currucoidesA brilliant blue bird of open country.
Broad-tailed hummingbirdSelasphorus platycercusIts wing trill buzzes through summer campgrounds.
American dipperCinclus mexicanusForages in rushing mountain creeks.
White-tailed ptarmiganLagopus leucurusAn alpine grouse of the high tundra.
Brown-capped rosy-finchLeucosticte australisA high-alpine finch mostly limited to Colorado and nearby mountains.

Reptiles & amphibians

Greater short-horned lizardPhrynosoma hernandesiA flat, spiny lizard of grasslands and woodland.
Plateau fence lizardSceloporus undulatusA common lizard of rocky and wooded areas.
Western terrestrial garter snakeThamnophis elegansFound near creeks and wetlands.
BullsnakePituophis cateniferA large, harmless snake of grasslands.
Plains spadefootSpea bombifronsEmerges to breed in temporary pools after heavy rain.
Tiger salamanderAmbystoma tigrinumLives in ponds and wetlands of the valley and mountains.
Western chorus frogPseudacris triseriataIts calls fill spring wetlands.
Northern leopard frogRana pipiensA spotted frog of valley wetlands.

Fish

Rio Grande cutthroat troutOncorhynchus clarkii virginalisA native trout restored to Medano Creek.
Rio Grande suckerCatostomus plebeiusA native fish of the park's creeks.

Insects & other invertebrates

Great Sand Dunes tiger beetleCicindela theatinaA fast, predatory beetle found only in this dune system; documented by NPS but not on the NPSpecies insect list used here.

Species totals are the park's certified NPSpecies checklist (occurrence: present).

Climate & When to Visit

Sitting near 8,000 ft, Great Sand Dunes has a cool, dry, high-desert climate with about 11 inches of precipitation a year. Temperatures stay fairly mild through summer, with July highs slightly above 80°F, but intense high-altitude sunshine heats the sand surface to around 150°F on summer afternoons. Nights are cool in summer and bitterly cold in winter.

Conditions are often calm, but strong winds rise in spring and along passing storm fronts, driving sand across the dunes. Summer monsoon moisture brings afternoon thunderstorms and lightning that are especially dangerous on the open dunes. In the mountains, snow lingers well into summer and feeds Medano Creek's late-spring surge.

Spring
Windy, variable and often cold, with snow in the mountains. Medano Creek typically peaks from late May to early June, with surges arriving about every 20 seconds.
Summer
Warm days, cool nights and very hot sand by midday. Afternoon thunderstorms are common, so explore the dunes in the morning or evening.
Autumn
Crisp, clear and calm, with golden cottonwoods and aspens. Sand temperatures are comfortable for hiking.
Winter
Cold and often clear, with occasional snow on the dunes. The valley has recorded lows of −25°F, and nights are frigid.

Weather hazards

Hot sand: Summer sand can reach about 150°F, so wear shoes and hike the dunes early or late in the day.
Lightning: The dunes are exposed, so get off them immediately when thunderstorms approach.
High winds and blowing sand: Spring winds and storm fronts can create blinding sand, so protect your eyes and gear.
Altitude and sun: At about 8,000 ft, sunlight is intense and dehydration comes quickly, so bring water and sun protection.
Cold nights: Temperatures drop sharply after sunset, so pack warm layers even in summer.

Great Sand Dunes Questions

When is the best time to visit Great Sand Dunes?

Late May to early June is ideal for seeing Medano Creek flowing, while September and October bring mild temperatures and golden aspens. Summer is busy and sand gets very hot by midday, so plan dune hikes for morning or evening.

How tall are the dunes?

The tallest dunes rise about 750 ft above the valley floor, making them the tallest in North America. Star Dune is often considered the tallest, while High Dune is a popular and more accessible climb.

How hot does the sand get?

On summer afternoons, the sand surface can reach around 150°F even though air temperatures may be only in the 80s. Wear closed-toe shoes and avoid midday hikes in summer.

How did the sand dunes form?

Sediment from the San Juan and Sangre de Cristo mountains collected in lakes and streams in the San Luis Valley. As those waters receded, prevailing winds carried the sand northeast, where it piled against the mountains and is trapped by opposing storm winds and recycling creeks.

What is the surge flow on Medano Creek?

In late spring, sand builds small underwater ridges in Medano Creek that break periodically and release pulses of water about every 20 seconds. In high-water years these surges can be as high as 20 inches.

Can I see wildlife at Great Sand Dunes?

Elk, mule deer, pronghorn and black bears live in the park and preserve, along with the Great Sand Dunes tiger beetle, found only here. Early morning is best for spotting animals and fresh tracks on the dunes.

More parks in the Rocky Mountains

← Great Basin National Park Great Smoky Mountains National Park →

Sources: www.nps.gov · www.nps.gov · www.nps.gov · irmaservices.nps.gov · en.wikipedia.org · Official NPS site